They are very restrictive with changes of status from B1/B2 to F1, and changing to F1 status (or any other nonimmigrant status) is not allowed unless the change of status was filed before the previous status expired. His B1/B2 status has expired and the visa is invalidated due to the overstay, so he is not eligible for a change of status. He must leave the US and apply at a consulate for the F1 visa.

They are very restrictive with changes of status from B1/B2 to F1, and changing to F1 status (or any other nonimmigrant status) is not allowed unless the change of status was filed before the previous status expired. His B1/B2 status has expired and the visa is invalidated due to the overstay, so he is not eligible for a change of status. He must leave the US and apply at a consulate for the F1 visa.